Assessment of tissue level of interleukin-9 in psoriasis and vitiligo

Background Psoriasis is a chronic, inflammatory, T-cell-mediated autoimmune disease. Vitiligo is an acquired depigmentary disease that occurs due to the loss of functional melanocytes from the epidermis. Interleukin (IL)-9 is a T cell-derived cytokine that was initially designated as a T helper2 cytokine. There is a link between the expression and action of IL-9 and pro-inflammatory cytokines tumor necrosis factor, IL-1, IL-17, and interferon-γ, suggesting that IL-9 is associated with the pathogenesis of autoimmune diseases. Objective To evaluate the tissue levels of IL-9 in patients with psoriasis and vitiligo in comparison with controls, to assess the possible role of IL-9 in the pathogenesis of these diseases. Patients and methods This case–control study included 30 patients with psoriasis, 30 patients with vitiligo, and 30 age-matched and sex-matched healthy controls. A skin biopsy was taken from all participants for evaluation of tissue IL-9 levels by enzyme-linked immunosorbent assay. Results Tissue IL-9 was significantly higher in patients with psoriasis (28.65±18.456) and patients with vitiligo (51.056±41.536) than controls (P=0.013 and P<0.001, respectively). In addition, it was significantly higher in patients with vitiligo than in patients with psoriasis (P=0.004). Conclusion This study suggests a possible role for IL-9 in the pathogenesis of psoriasis and vitiligo by documenting significantly higher tissue levels in patients than in controls.